1. Field of the Invention
This disclosure is generally related to fuel cell systems for generating electrical energy, and more particularly to the startup of fuel cell systems.
2. Description of the Related Art
A fuel cell system of this class is known from DE 199 51 584 A1. The use of the two synchronous machines such as two permanent-magnet electric motors, as specified in DE 199 51 584 A1, eliminates the previous need for DC/DC converters, so that the overall fuel cell system becomes less complicated and thus better suited for practical application.
A drawback of this approach is that the synchronous machines require collector rings for field excitation, which are subject to high wear and tear, and thus present a problem to the practical commercial embodiments of the proposed system. A further disadvantage of this approach is the requirement of an additional controller, which results in higher costs and makes the resulting system unnecessarily complicated.
Many applications for fuel cell based power generation systems are extremely price sensitive. Further, high reliability must be demonstrated to establish the fuel cell based power generation system market. Thus, a fuel cell based system for the generation of electrical energy that possesses a simple design and at the same time ensures reliable starting and problem-free operation of the fuel cell is desirable.